iio: core: add missing IIO_MOD_H2/ETHANOL string identifiers

Add missing strings to iio_modifier_names[] for proper modification
of channels.

Fixes: b170f7d (iio: Add modifiers for ethanol and H2 gases)
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -130,6 +130,8 @@ static const char * const iio_modifier_names[] = {
 	[IIO_MOD_PM2P5] = "pm2p5",
 	[IIO_MOD_PM4] = "pm4",
 	[IIO_MOD_PM10] = "pm10",
+	[IIO_MOD_ETHANOL] = "ethanol",
+	[IIO_MOD_H2] = "h2",
 };
 
 /* relies on pairs of these shared then separate */